WAR FOR THE UNION! Front of Charleston. NEW YORK, Dec. 19. The Tr ibmt'$ Folly Island correspon dent virile, undrr date r Dec. 13, (hat on Saturday omriiitifl, while the lido wss retwdlnp,no ofihs private of (ho 8d Rhode Island Ballcry discovered, Irom Tort Pntnun, on th bench what he though. l be brass field pice. He sk rd and obtained prrmUslcn to gn and oe. It armed liimeslf Willi a apadv, and In a fcw wiinuit riVi'i.Icd a besutiful IS-pounder. Twelve men werr Inline- iliutely detailed lo carry it into thu lorl, which ae dmn aucccsafully uinlcr brisk fir from M..u1lrlu. As soon a It was in th furl, It wae mounted In a ood Jioailioii, ready at moment's notice lo be used against It old Irientit. Tht spade, In tho couraa oftheday, nun lit to the rur.'aie fi hundred . rounds of solid shot that just suited the ralibrr or the piece. It la thuujil that the rebels before rvsemtinff Gri i'L'. huri- rda'qua t ty ol ammunition ofall soils. A , lew oate will drrido tlio mailer. Tht storm and...